On this project, researchers at the University of Chicago and the University of New Hampshire will develop a parameterization of the shallow water carbon cycle for inclusion into global-scale ocean carbon cycle models (henceforth referred to as GCMs). GCMs are, by necessity, too coarsely gridded to resolve the physics and biochemistry of shallow waters and therefore suffer in their treatment of processes like the burial of organic carbon, denitrification, and CaCO3 compensation. As a result, they fail to incorporate the effect of the ocean margins on the global ocean carbon cycle and climate. Numerous regional studies have examined the role of the continental shelves in the export of carbon, iron, and as a sink for nitrogen. It therefore seems timely, to synthesize the data from such field studies, examine the sensitivity of sediment-water fluxes and across-shelf biogeochemical transport to various parameters, and build a parameterization that will capture the contribution of the ocean margins in the global ocean carbon cycle over glacial-interglacial time scales.
As a first step, this project will focus on building such a parameterization based on two regions that have been extensively studied, but differ in their characteristics: The eastern US continental shelf and the western US coasts of Oregon and California. It will act in response to parameters like the width and depth of continental shelves, changes in wind stress and open ocean circulation, and continental runoff, while using the Muds model to estimate the sediment-water fluxes. The sensitivity of coastal biogeochemical fluxes to these parameters will be tested with a high resolution coastal ocean circulation model configured to these sites, before generalizing to other regions. The parameterization will then be coupled to a GCM at every coastal grid point, providing the chemical fluxes to and from coastal waters and sediments. The full model (GCM + coastal submodel) will be used to assess the effect of shallow waters on the carbon cycle over glacial cycles while responding to glacial / interglacial sea level change. It will also be used to make future assessments of the shallow water CaCO3 dissolution response to fossil fuel CO2.
